Abstract
Stabilizing the eastern, migratory population of monarch butterflies (Danaus plexippus) is expected to require substantial habitat restoration on agricultural land in the core breeding area of the Upper Midwestern U.S. Previous research has considered the potential to utilize marginal land for this purpose because of its low productivity, erodible soils, and high nutrient input requirements. This strategy has strong potential for restoring milkweed (Asclepias spp.), but may be limited in terms of its ability to generate additional biophysical and socioeconomic benefits for local communities. Here we explore the possibility of restoring milkweed via the creation of continuous riparian buffer strips around perennial and intermittent streams throughout the region. We use a GIS-based analysis to consider the potential of several different buffer-width scenarios to meet milkweed restoration targets. We further estimate the ability of these habitat areas to provide additional functionality in the form of crop pollination and water quality regulation across the entire region. Finally, we estimate the conservative economic value of these ecosystem services and compare it with the lost value of crops associated with each scenario. Results suggest that riparian buffers could be used to meet 10-43% of the total milkweed restoration target of 1.3 billion new stems with moderate management. The value of water quality and pollination benefits provided by buffers is estimated to exceed costs only for our smallest buffer-width scenario, with a cost-benefit ratio of 1:2.05. Larger buffer widths provide more milkweed, but costs to farmers exceed the benefits we were able to quantify. The large-scale restoration of multifunctional riparian corridors thus has the potential to add milkweed stems while also providing a variety of other valuable benefits. This suggests the potential to leverage monarch habitat restoration efforts for the benefit of a wider variety of species and a broader coalition of beneficiaries.
Highlights
The migration of monarch butterflies throughout eastern North America is celebrated across the continent, from festivals to back yards to school yards
The loss of milkweed species that developing monarch larvae require for food, due to changing agricultural practices in the U.S is thought to be an important cause of monarch population declines (Pleasants and Oberhauser, 2013; Flockhart et al, 2015; Oberhauser et al, 2017; Pleasants, 2017; Saunders et al, 2017; Thogmartin et al, 2017b) among many other contributing factors (Ries et al, 2015; Inamine et al, 2016; Thogmartin et al, 2017a)
Despite the abundance of ecosystem services produced by riparian corridors, we found no studies that have attempted to quantify them at a regional, landscape scale
Summary
The migration of monarch butterflies throughout eastern North America is celebrated across the continent, from festivals to back yards to school yards. Monarch Habitat From Riparian Buffers for income (Haefele et al, 2018) Despite their importance to people, the monarch population progressively declined over 2 decades to its lowest recorded level in 2014 (Vidal and Rendón-Salinas, 2014) and despite a subsequent rebound it remains at an elevated risk of extinction (Semmens et al, 2016). An estimated 1.3–1.6 billion milkweed stems must be restored to the Upper Midwestern landscape to meet the 6-ha conservation goal (Pleasants, 2017; Thogmartin et al, 2017a). A geospatial analysis conducted to explore milkweed restoration scenarios found it impossible to reach this target without participation from the agricultural sector, which occupies 77% of all potential monarch habitat in the Upper Midwest (Thogmartin et al, 2017a). All non-agricultural sectors combined could accommodate up to 62% of the 1.3 billion stem milkweed target, necessitating at least 500 million stems on agricultural land. Thogmartin et al (2017a) suggested restoring this number of stems could be accomplished by retiring the least productive farmland and/or through changes in agricultural practices that may allow the persistence of milkweed
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